Generally, within the technical field of electrically controlled shock absorbers a valve arrangement is used to control a flow of damping medium between a compression chamber and a rebound chamber during a reciprocal motion of a piston in a damping medium filled chamber of the shock absorber. The piston, via a piston rod, is connected either to a wheel or a chassis, whereas the chambers are connected to one of the wheel or chassis that the piston is not connected to. During a compression stroke the piston moves axially in a direction towards the compression chamber and thereby pressurizes the damping medium in the compression chamber. During a rebound stroke, the piston moves axially towards the rebound chamber, i.e. in the opposite direction, and thereby pressurizes the damping medium in the rebound chamber. In accordance with the function of the shock absorber, the pressurized damping medium needs to be transferred from the pressurized chamber to the other chamber, i.e. from the compression chamber to the rebound chamber or vice versa. The flow of damping medium needs to be controlled to obtain a damping effect of the piston and thus the shock absorber, i.e. to damp relative motion between the wheel and chassis.
The control of the pressure in the flow of damping medium in the shock absorber may depend on the pressure created by a valve arrangement. Pressure regulators in shock absorbers may be provided with an axially movable or deflectable valve member, such as a washer, cone or shim that acts against a seat part. The pressure control is achieved by equilibrium or balance of forces, for example equilibrium between a pressure and/or flow force acting on the valve member in one direction and counteracting or opposing forces, such as one or more of a spring force, friction force or pilot pressure force acting on the valve member in the opposite direction. When the piston of the shock absorber moves at a certain speed such that the pressure and/or flow force become greater than the opposing or counteracting forces, the movable valve member is forced away from the seat part, thereby opening a flow passage. Thus, the movable valve member is forced to open at a stroke defined as a function of the flow produced by the pressure acting on the regulating area of the pressure regulator.
Some state of the art valve arrangements use a slidably arranged control valve member for regulating a flow. The regulated flow of such slidably arranged control valve members may either be the main flow, or a by-pass flow for allowing a flow parallel to the main flow between the compression and the rebound chamber.
A problem with this type of valve members, often being pressure relieved and biased by a pressure balance and/or spring arrangement valves, is that the available force for adjusting the axial position normally is low which makes them sensitive to forces acting on the valve member. Thus, such valve arrangements are very susceptible to disturbance during operation.
Therefore, there is a need for a valve arrangement for shock absorbers with increased operating reliability.